They said the current roll-out is for a subset of US users, but who knows what their future plans are.

(I'm going from memory here -- they deleted the relevant text on mozilla.org, replacing it with the apology paragraph).

https://support.mozilla.org/en-US/kb/navigate-web-faster-fir...

edit: Found an archive snapshot:

https://archive.is/E7opj

"Firefox Suggest is currently available for a limited number of users in the U.S. only" (deleted text)

I'd be surprised if the US didn't have the largest amount of firefox users, even if it isn't the majority of all users worldwide. I couldn't find any data to back that up, though, since the public site[0] has no per-country statistics.

0: https://data.firefox.com/

Very late second reply comment to you: I've found confirmation that

>"In the future Firefox Suggest online will likely be expanded to other locales/populations."

https://bugzilla.mozilla.org/show_bug.cgi?id=1723860#c5